1. Field of the Invention
The present invention relates to a static electricity measuring system.
2. Description of the Related Art
Static electricity measuring apparatuses are disclosed in Japanese Unexamined Patent Publication (Kokai) 5-126,883 (hereinafter referred to as the "'883 publication"), entitled "Correcting Apparatus For Powder Electric Charge Measuring Device"; and Japanese Examined Patent Publication (Kokoku) 7-1,291 (hereinafter referred to as the "'291 publication"), entitled "Apparatus For Detecting Electric Potential Of Charged Powder And Apparatus For Controlling Charging." The contents of these applications are incorporated herein by reference in their entirety.
The '883 publication discloses a correcting apparatus for correcting a measuring error in a measuring device when electric charge of conductive powder for a copying machine is measured. In this apparatus, the amount of electric charge of the toner is measured by a suction type Faraday cage when the voltage is applied to the toner. The measured value is corrected by comparing the measured value with a reference value of a reference Faraday cage.
In this apparatus, however, toner sample is removed from the copying machine and subsequently the amount of electric charge of the toner is measured. Thus, the amount of electric charge of the toner cannot be measured in the copying machine in real time.
The '291 publication discloses an apparatus for detecting electric potential of charged powder flowing in a fluid dryer. In this apparatus, an electric potential detecting unit is attached to an outer side wall of the dryer. The detecting unit detects the electric potential through a detecting hole which faces a window provided in the outer side wall of the dryer. In order to prevent the flowing powder from entering the inside of the detecting unit through the detecting hole, air is supplied between the window and the detecting hole to form an air layer therebetween which serves as a barrier.
In this apparatus, however, the entrance of the powder to the detecting unit. is not effectively prevented. Accordingly, the apparatus does not precisely detect electric potential of the charged flowing powder.